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2 sheets -sheet 1.

F. J. .SPRAGUE.

ELECTRO DYNAMIC MOTOR.

(No Model.)

Patented June 30, 1885.

INVENTU UNITED STATES PATENT OrEIcE.

FRANK J. SPRAGUE, OF NEIV YORK, N. Y., ASSIGNOR TO THE SPItAG-UE ELECTRIC RAILWAY AND MOTOR COMPANY.

ELECTRO-DYNAMIC MOTOR.

FDPECIPICATIOET forming part. of Letters Patent No. 321,148, dated June 30, 1885.

Application filed March 3, 1885. (N0 model T0 aZZ whom it ntay concern:

Be it known that I, FRANK J. SPRAGUE, of New York, in the county and State of New York, have invented a certain new and useful Improvement in Electro-Dynamic Motors, of which the following is a specification.

This invention relates to a method of opera tion for electro-dynamic motors on circuits of constant difference of potential. Such method consists in first introducing the motor into circuit with a very strong field and with a small difference of potential at the terminals of the armature-circuit, so that the motor starts slowly; then progressively raising the armaturecircuit potential until that circuit is brought up to full potential, and then, to still further increase the speed,weakening the field-magnet strength. I have'devised an an paratus in which all these operations affecting the armature and field circuits are performed by a single commutator-arm,which apparatus I have found to be a convenient one for carrying the above-described method into effect. This apparatus is illustrated in the accompanying drawings, in which Figure 1 is a diagram of a motor with its connections and of the apparatus embodying my invention; Fig. 2, a vertical longitudinal section of the commutator which I employ, with a diagram of the connections 3 Fig. 3, a vertical transverse section of the commutator, and Fig. 4 a top view of the commutator.

A is a shuntwound electro-dynamic motor. 1 2 are the line-conductors from which said motor derives current.

B is a series of resistance-coils for the armature-circuit, the terminals of which are brought to contact-blocks a a, and G is a similar series of resistances for the field-circuit connected with contacts I) 1).

Situated opposite the contacts a c in a line with contacts 0 bis a long contact-blocl ,c,con-, nected in the field-circuit, and opposite the contacts 12 b in line with contacts a a is a similar long cont-act-blcck, d, in the armature-circuit.

The contacts a c and (l are mounted in the form of an are on an insulating-strip, D, and contacts I) b and c are similarly mounted on strip E. The contacts are preferably of the form shown, being supported off from the strip,so as to enter between the jaws of forked contacts eand e, which are carried by a metal arm, F, pivoted at f and working back and forth between the two series of contacts. To this arm F is permanently connected one of the terminals of the supplying-circuit. WVhen the contacts a e are at the highest position in the diagram Fig. 1, it will be seen that all the resistance-coils a a are in the armaturecircuit; but there are none in the field-circuit. Consequently there is a strong field-magnet and weak armature when the motor is started by throwing in switch 9. On then moving the contacts 6 0 down resistance is cut out of the armaturecircuit, while as contact 0 is moving on thelong block (I there is no change in the field-circuit. Thus the armature-circuit is gradually raised to the full potential, which is reached when the contact 6 reaches the lowest of the contacts (L. Then to weaken the field, and still further increase the speed or power,or both,of the motor,the contacts 6 c are moved further down, and as they pass from one contact I) to another resistance-coils G are placed in circuit and the field is gradually weakened, while the armature-circuit is not affected, because contact 6 is moving on the long block 0. The ends of the two long blocks extend opposite each other, so that circuit is maintained in passing from the armature-resistance contacts to the field-resistance contacts. In practice these efl'ects are produced by moving the pivoted arm F along the two series of contacts. The motor is thus made to start slowly, and then to gradually increase its speed up to the maximum. IVhile the motor is running its field-magnet may be regulated without aifecting the armature-current by changing the position of the moving contacts between contact (I and contacts Z) b.

It will be understood that in the section Fig.2 only the fieldcircuit resistance contacts can be seen; hence the wire which leads to the armature-resistance contact is broken off in this figure at h.

G is a switch for reversing the armature circuit, and H a similar switch for reversing the field-circuit.

I do not claim herein the apparatus de 2. The method of operating an clectro-dy- 15 namic motor, which consists in starting the motor with resistance in its armature-circuit and little or no resistance in its field-circuit, gradually cutting out resistance from the armature-circuit, and then graduallyincreasing the resistance of the field-circuit, substantially as set forth.

This specification signed and witnessed this 16th day of February, 1885.

FRANK J. SPRAGUE.

\Vitnesses:

A. \V. KIDDLE, E. G. ROXVLAND. 

